Personal-care apparatus comprising a capacitive on/off switch

Abstract

A personal-care apparatus comprises a load (LD) and a switch (SW), which load (LD) and which switch (SW) are coupled in series between a first (1) and a second (2) supply terminal for receiving an alternating voltage, the personal-care apparatus further comprising a rectifying circuit (RC) for converting the alternating voltage into a direct voltage, and a safety circuit (SC), which is coupled between a third (3) and a fourth (4) supply terminal for receiving the direct voltage and which comprises a capacitive sensor (CS) for the detection of the presence of a part of a human body in the proximity of the personal-care apparatus, the safety circuit being adapted to control the switch (SW) in response to said detection.

We claim: 
     
       1. A personal-care apparatus including means for being held by a user, comprising: first and second supply terminals for receiving an alternating voltage;   a load;   a switch coupled to the load for activating and deactivating the load by controlling the alternating voltage to the load, the load and the switch being coupled in series between the first and the second supply terminals;   a rectifying circuit having third and fourth supply terminals, for converting the alternating voltage into a direct voltage and for supplying the direct voltage across the third and fourth supply terminals; and   a safety circuit coupled between the third and fourth supply terminals for receiving the direct voltage, the safety circuit including (i) a capacitive sensor for detecting the presence of a human body part in proximity to the personal-care apparatus, and (ii) means for controlling the switch such that the load is activated if the capacitive sensor senses a user holding the personal-care apparatus and the load is deactivated if the capacitive sensor senses that the user is no longer holding the personal-care apparatus, regardless of the orientation of the personal-care apparatus.   
     
     
       2. A personal-care apparatus as claimed in claim 1, which apparatus comprises a handle, characterized in that the capacitive sensor is arranged near the handle. 
     
     
       3. A personal-care apparatus as claimed in claim 2, wherein the safety circuit further comprises (i) a first oscillator including the capacitive sensor, and an output, (ii) a frequency-to-control-signal converter having an input coupled to the output of the first oscillator and having an output, and (iii) a first switching element having a control current path coupled to the output of the frequency-to-control-signal converter and having a main current path coupled to the switch. 
     
     
       4. A personal-care apparatus as claimed in claim 2, wherein the personal-care apparatus further comprises an interrupt switch operable for switching ON and OFF the load when the switch is in a state which activates the load. 
     
     
       5. A personal-care apparatus as claimed in claim 1, characterized in that the safety circuit further comprises (i) a first oscillator including the capacitive sensor, and an output, (ii) a frequency-to-control-signal converter having an input coupled to the output of the first oscillator and having an output, and (iii) a first switching element having a control current path coupled to the output of the frequency-to-control-signal converter and having a main current path coupled to the switch. 
     
     
       6. A personal-care apparatus as claimed in claim 5, characterized in that the safety circuit further comprises (i) a second oscillator including a capacitor and an output, and (ii) a second switching element having a control current path coupled to the output of the second oscillator and having a main current path coupled in parallel with the main current path of the first switching element. 
     
     
       7. A personal care apparatus as claimed in claim 6, wherein the switch includes a control current path serially coupled to the main current path of the first switching element, and a main current path coupled to the load. 
     
     
       8. A personal-care apparatus as claimed in claim 6, wherein the personal-care apparatus further comprises an interrupt switch operable for switching ON and OFF the load when the switch is in a state which activates the load. 
     
     
       9. A personal-care apparatus as claimed in claim 5 wherein the personal-care apparatus further comprises an interrupt switch operable for switching ON and OFF the load when the switch is in a state which activates the load. 
     
     
       10. A personal-care apparatus as claimed in claim 1 characterized in that the personal-care apparatus further comprises an interrupt switch operable for switching ON and OFF the load when the switch is in a state which activates the load. 
     
     
       11. A personal-care apparatus as claimed in claim 5, characterized in that the safety circuit further comprises an indicator element for generating a warning signal, the indicator element being serially coupled to the main current path of the first switching element. 
     
     
       12. A personal-care apparatus as claimed in claim 11 wherein the safety circuit further comprises (i) a second oscillator including a capacitor and an output, and (ii) a second switching element having a control current path coupled to the output of the second oscillator and having a main current path coupled in parallel with the main current path of the first switching element. 
     
     
       13. A personal care apparatus as claimed in claim 11, wherein the switch includes a control current path serially coupled to the main current path of the first switching element, and a main current path coupled to the load. 
     
     
       14. A personal-care apparatus as claimed in claim 11, wherein the personal-care apparatus further comprises an interrupt switch operable for switching ON and OFF the load when the switch is in a state which activates the load. 
     
     
       15. A personal-care apparatus as claimed in claim 5, characterized in that the switch includes a control current path serially coupled to the main current path of the first switching element, and a main current path coupled to the load. 
     
     
       16. A personal-care apparatus as claimed in claim 15, wherein the personal-care apparatus further comprises an interrupt switch operable for switching ON and OFF the load when the switch is in a state which activates the load. 
     
     
       17. A safety circuit for use in a personal-care apparatus including (i) means for being held by a user, (ii) first and second supply terminals for receiving an alternating voltage, (iii) a load, (iv) a switch coupled to the load for activating and deactivating the load by controlling the alternating voltage to the load, the load and the switch being coupled in series between the first and the second supply terminals, and (iv) a rectifying circuit having third and fourth supply terminals, for converting the alternating voltage into a direct voltage and for supplying the direct voltage across the third and fourth supply terminals, the safety circuit being coupled between the third and the fourth supply terminals and comprising: a capacitive sensor for detecting the presence of a human body part in proximity to the personal-care apparatus; and   means for controlling the switch such that the load is activated if the capacitive sensor senses a user holding the personal-care apparatus and the load is deactivated if the capacitive sensor senses that the user is no longer holding the personal-care apparatus, regardless of the orientation of the personal-care apparatus.   
     
     
       18. A safety-circuit as claimed in claim 17, wherein the means for being held by a user comprises a handle and the capacitive sensor is arranged near the handle. 
     
     
       19. A safety-circuit as claimed in claim 17, characterized in that the safety circuit further comprises (i) a first oscillator including the capacitive sensor and an output, (ii) a frequency-to-control-signal converter having an input coupled to the output of the first oscillator and having an output, and (iii) a first switching element having a control current path coupled to the output of the frequency-to-control signal converter and having a main current path coupled to the switch. 
     
     
       20. A safety-circuit as claimed in claim 19, characterized in that the safety circuit further comprises an indicator element for generating a warning signal, the indicator element being serially coupled to the main current path of the first switching element. 
     
     
       21. A safety-circuit as claimed in claim 19, characterized in that the safety circuit further comprises (i) a second oscillator including a capacitor and an output, and (ii) a second switching element having a control current path coupled to the output of the second oscillator and having a main current path coupled in parallel with the main current path of the first switching element. 
     
     
       22. A safety-circuit as claimed in claim 19, characterized in that the switch includes a control current path serially coupled to the main current path of the first switching element, and a main current path coupled to the load. 
     
     
       23. A safety-circuit as claimed in claim 17, characterized in that the personal-care apparatus further comprises an interrupt switch operable for switching ON and OFF the load when the switch is in a state which activates the load. 
     
     
       24. A personal care apparatus including means for being held by a user, comprising: first and second supply terminals for receiving an alternating voltage;   a load;   a switch coupled to the load for activating and deactivating the load by controlling the alternating voltage to the load, the load and the switch being coupled in series between the first and the second supply terminals;   a rectifying circuit having third and fourth supply terminals, for converting the alternating voltage into a direct voltage and for supplying the direct voltage across the third and fourth supply terminals; and   a safety circuit coupled between the third and the fourth supply terminals for receiving the direct voltage, the safety circuit including (i) a capacitive sensor for detecting the presence of a human body part in proximity to the personal-care apparatus, (ii) a first oscillator having an output and including the capacitive sensor, for oscillating at a first frequency and supplying a first signal to its output if the capacitive sensor senses a human body part in proximity to the personal-care apparatus, and for oscillating at a second frequency and supplying a second signal to its output if the capacitive sensor does not sense a human body part in proximity to the personal care apparatus, and (iii) a frequency-to-control-signal converter coupled to the first oscillator for receiving the first and second signals and for converting the first and second signals to a first and a second control signal respectively, which control signals control the switch such that the alternating voltage is supplied to the load if the first control signal is generated by the frequency-to-control signal converter which indicates the user has picked up the personal care apparatus, and for causing the alternating voltage to be removed from the load if the second control signal is generated by the frequency-to-control signal converter which indicates the user is no longer holding the personal care apparatus.   
     
     
       25. A personal care apparatus as claimed in claim 24, wherein the frequency-to-control signal converter includes a first capacitor coupled to the first oscillator, a diode coupled to the first capacitor, and a second capacitor coupled to the diode and wherein the first capacitor is chosen such that only one of the first and second signals is passed by the first capacitor, the passed signal being restored to a DC level by the diode, the second capacitor being charged by the DC level to produce the first control signal, and the second control signal being produced by the second capacitor not being charged. 
     
     
       26. A personal care apparatus as claimed in claim 25, wherein the safety circuit further includes a first switching element coupled to receive the first and the second control signals, and having a main current path coupled to the switch. 
     
     
       27. A personal care apparatus according to claim 25, wherein the capacitive sensor includes a first plate coupled to the means for being held. 
     
     
       28. A personal care apparatus according to claim 26, wherein the safety circuit further comprises an indicator element, for generating a warning signal, the indicator element being serially coupled to the main current path of the first switching element. 
     
     
       29. A portable personal-care apparatus including means for being held by a user, comprising: a first and a second supply terminal for receiving a alternating voltage;   a load;   a switch, the load and the switch being coupled in series between the first and the second supply terminals;   a rectifying circuit having third and fourth supply terminals, for converting the alternating voltage into a direct voltage and for supplying the direct voltage between the third and fourth supply terminals; and   a safety circuit coupled between the third and fourth supply terminals for receiving the direct voltage, the safety circuit including a capacitive sensor for detecting the presence of a human hand and being adapted to control the switch so as to enable activation of the apparatus when the apparatus is picked up by a user and so as to deactivate the apparatus when the user is no longer holding the apparatus, regardless of the orientation of the apparatus.